1. Field of the Invention
The present invention relates to a wire bonding apparatus.
2. Description of the Related Art
As wire bonding apparatuses for connecting bonding wires (Au) between bonding pads of semiconductor chips and lead-out terminals of packages, there are a thermopressing type, an ultrasonic thermopressing type and an ultrasonic type. The ultrasonic thermopressing type wire bonding apparatus are widely used in the manufacture of quad flat packages (QFPs) having less than 200 pins.
In an ultrasonic thermopressing type wire bonding apparatus, a bonding pad of a semiconductor chip is heated to about 150 to 300xc2x0 C., and a gold ball formed by gold wire is pushed down by a capillary onto the bonding pad. Then, ultrasonic waves are performed upon the capillary, so that the gold ball is deformed to break oxide on the bonding pad, thus surely connecting the gold ball to the bonding pad.
The above-mentioned wire bonding apparatus uses an ultrasonic horn for transmitting ultrasonic waves to the capillary. That is, a prior art wire bonding apparatus is constructed by a horn driver for generating ultrasonic waves, a capillary, an ultrasonic horn including a symmetrical section fixed to the horn driver and an asymmetrical section having an end for mounting the capillary (see JP-A-2000-340598). This will be explained later in detail.
In the above-described prior art wire bonding apparatus, however, since the asymmetrical section is tapered, spurious vibration of the capillary occurs so as to reduce the accuracy of the bonding operation.
It is an object of the present invention to provide a wire bonding apparatus capable of improving the accuracy of the bonding operation.
According to the present invention, in a wire bonding apparatus including a horn driver for generating ultrasonic waves, a capillary, an ultrasonic horn formed by a symmetrical section fixed to the horn driver and an asymmetrical section having an end for mounting the capillary, the asymmetrical section is constructed by a spurious vibration suppressing structure for suppressing a vibration component of the ultrasonic horn perpendicular to a propagation direction of the ultrasonic waves within the ultrasonic horn.